The heterogeneous rate constants (ks) for the oxidation of iron- and ruthenium-bipyridine complexes, [Fe(bpy)3]2+/3+ and [Ru(bpy)3]2+/3+ have been determined using Nicholson’s method in imidazolium-based ionic liquids with five different types of cation/anion over a range of temperature from 298–318 K. The heterogeneous rate constants of these redox reactions range from 10−4 to 10−3 cm s−1, depending on the dynamic viscosity and type of cation/anion of the ILs. Marcus-Hush theory is used to explain the activation energies, Ea. Similar activation energies are found for the Fe-bipyridine and Ru-bipyridine complexes indicating that inner-sphere reorganization energy has only a small influence. For the calculation of the solvent-dependent outer sphere reorganization energy a dipole-free expression is used, adopted to the different dielectric properties of ionic liquids compared to organic solvents. i-Ru drops have been compensated using the corresponding experimental uncompensated Ru-values obtained from temperature dependent Bode-plots.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry